1. Field of the Invention
This invention relates to a video endoscope provided at the tip of the insertable part in parallel with an imaging apparatus and a treating instrument channel through which a laser treating instrument can be inserted.
2. Related Art Statement
This kind of video endoscope has an elongated flexible part, a bendable part and rigid tip part connected sequentially to this flexible part at the tip to form an insertable part, has an operating part connected to this insertable part at the rear end and a flexible: universal cord extended sidewise from this operating part and is provided in the above-mentioned operating part with a treating instrument inserting port communicating with the treating instrument channel provided in the above mentioned operating part. Also, the above mentioned video endoscope is provided at the tip of the insertable part in parallel with an imaging apparatus including an observing window, image-forming optical system and solid state imaging device, a treating instrument channel through which a treating instrument is to be passed and an illuminating optical system-- including an illuminating window and light guide fibers for illuminating a part to be inspected. Also, this endoscope is provided in the treating channel with a channel tube.
In the case of making a laser therapy by using such video endoscope, a laser treating instrument (laser probe) is inserted through the treating instrument inserting port and is directed at the tip to a desired part, for example, by bending the bendable Part and the part is imaged by the imaging apparatus and is laser-cauterized while the image is being observed in a monitor.
Now, there has been a problem that, in the case of the above mentioned laser-cauterization, a reflected laser light of the laser light radiated from the laser probe tip will enter the imaging apparatus through the observing window provided in the insertable part tip of the video endoscope and will be depicted in the monitor and the part of the object to be inspected will become hard to see.
In order to cope with this problem, there is suggested in Japanese patent applications laid open Nos. 148225/1988 and 265934/1985 a prior art wherein, in order to prevent a reflected laser light from entering an imaging device, an optical system leading to the imaging device is provided with an optical filter intercepting a laser light but transmitting a visible light.
However, in the above described prior art example, the laser light entering through the observing window at the insertable part tip can be coped with but the laser light entering the imaging device through the other course than the course leading to the imaging apparatus from the observing window can not be coped with.
That is to say, in the video endoscope, there is a disadvantage that, when the bendable part provided in the insertable part is bent, the laser probe will also bend, a laser light leaking from the laser probe, for example, in the bent part or a laser light emitted from the laser probe tip, is reflected and enters the treating instrument channel from the outlet opening leaking on the imaging apparatus side out of the peripheral wall of the treating instrument channel and will enter the imaging device, which causes the monitor image to become black and a produce flare or blooming.